A massive magnitude 8.8 earthquake struck off the coast of Russia on Tuesday, sparking tsunami warnings -- and evacuations of coastal areas -- in Hawaii and alerts for other areas of the U.S. West Coast.
In a message posted on social media, President Donald Trump urged people to "STAY STRONG AND STAY SAFE" and to monitor updates on the tsunami.gov online dashboard.
In Hawaii, the National Weather Service called for "urgent action" to protect lives and property.
Officials there urged residents to leave beaches and evacuate low-lying areas for higher ground or to take shelter on at least the fourth floor of a building. Sirens sounded across the Hawaii islands 10 minutes after each hour for the three hours leading up to the expected impact as a part of a statewide warning system.
The first tsunami waves were forecast to reach Hawaii just after 7:15 p.m. local time -- or 1:15 a.m. ET. The initial waves were expected on the Kauai coast, with effects on Hawaii island about 20-30 minutes later.
Speaking at a press conference less than an hour before the waves were expected to hit, Hawaii Gov. Josh Green said -- based on indications from other areas in the Pacific, the waves had already passed through -- officials in Hawaii were braced for a "significant wave" measuring 6 feet total, from peak to trough. "That means a 3-foot wave riding on the top of the ocean," Green said.
All shores of the island are at risk because tsunami waves wrap around islands, officials said.
"The danger can continue for many hours after the initial wave as subsequent waves arrive. Tsunami heights cannot be predicted and the first wave may not be the largest," the National Weather Service said in an alert.
"It is not just a 3-foot wave, it is a forceful wall of water," the governor said, adding that it's possible such a wave could knock down utility poles and leave debris strewn in its wake.
Amid earlier reports of traffic gridlock as residents evacuated the shoreline, the governor said he thought there was plenty of time for people to reach higher ground and that it appeared traffic was already easing.
In an interview with ABC Honolulu affiliate KITV, Honolulu Mayor Rick Blangiardi urged residents to move to higher ground.
"We need people to stay calm but also to act accordingly. If you can get to higher ground if you're in a low-lying area, please do that." He urged caution on the roads amid "bumper-to-bumper traffic" during evacuations.
Tsunami alerts for U.S. West Coast -- and elsewhere in the world
In the wake of the quake, a tsunami warning was also issued for part of Alaska's Aleutian Islands and Northern California, from Cape Mendocino -- located about 200 miles north of California -- to the Oregon border. The rest of the California coast, as well as Oregon and Washington, are under a tsunami advisory, while the threat is being evaluated.
The U.S. territories of Guam and American Samoa are also under a tsunami advisory, according to USGS.
The intense quake occurred about 85 miles off the east coast of Russia's Kamchatka Peninsula with a depth of nearly 12 miles, according to the U.S. Geological Survey. It was one of the most powerful earthquakes ever recorded by the agency, which upgraded its magnitude from initial reports of 8.0 and 8.7.
Magnitude 6.3 and 6.9 aftershocks were also reported in the area, according to USGS.
An advisory was also issued for Japan's Pacific Coast regions from Hokkaido to Kyushu.
Japan's meteorological agency warned that a tsunami about 1 meter (3 feet) high is expected to reach Hokkaido in the north around 10:00 a.m., local time, with waves arriving later in the day along parts of eastern Honshu and Kyushu in the south.
People are warned to stay away from the coast and river mouths and not to approach the water to observe.
Ecuador and Chile are also under tsunami alerts, according to local officials.
A tsunami warning means that a tsunami that could cause widespread, dangerous flooding and powerful currents is expected. A tsunami watch means a distant earthquake has occurred and a tsunami is possible.
ABC News' Bonnie Mclean, William Gretsky, Anthony Trotter and Mireya Villarreal contributed to this report.
This is a developing story. Please check back for updates.
